Polyester-based adhesive are known but limited. U.S. Pat. No. 3,378,630 describes a thermosetting adhesive comprising a saturated polyester resin and small amounts of melamine-formaldehyde resin, epoxy resin, flexibilizer and antioxidant. The adhesive can be applied to a fibrous backing to make an adhesive tape useful in electrical insulation applications.
U.S. Pat. No. 3,772,064 also describes a polyester-based thermosetting adhesive. The polyester is derived from a low molecular weight dihydric or trihydric polyol, a difunctional aliphatic acid or its corresponding halide or anhydride and a polyfunctional aromatic acid or its corresponding halide or anhydride. This adhesive also can be applied to a fibrous backing to make an adhesive tape useful in electrical insulation applications.
U.S. Patent Application Publication No. 2012/0202058 describes an adhesive sheet for surface protection comprising a substrate and an adhesive layer. The adhesive comprises (i) polyester containing at least a lactic acid unit, a dibasic acid unit, and a glycol unit, and (ii) a crosslinking agent.
Many of these adhesive compositions claim to be “pressure sensitive,” but do not meet the practical definition of being a pressure-sensitive adhesive (PSA) as they do not satisfy the Dahlquist criteria for adhesive stiffness. Instead, these materials are better classified as hot-melt or structural type adhesives. One example of a “pressure-sensitive” adhesive comprising polyester is demonstrated in U.S. Patent Application Publication No. 2012/0301717. The invention of this publication is described as a polyester adhesive comprising aliphatic biodegradable polyester having a low weight average molecular weight (Mw) of 1×103 to 20×103 as the main component and a tri- or polyfunctional epoxy compound as a crosslinking agent. Such polyesters do not have the same chemical and mechanical resistance as those of traditional condensation polyesters comprising petroleum-derived, non-degradable aromatic diacids (e.g., terephthalic acid and isophthalic acid) with higher weight average molecular weights (40-400 kDa).